The surface area of filter media is a major factor in determining flow resistance (i.e., pressure drop) and loading capacity of a pleated filter. The surface area of a pleated filter media is determined by the size of the pleated filter, the depth of the pleats, and the pleat density. Since the external dimensions of pleated filters are often restricted by the particular application, the number of pleats per inch (pleat density) can be increased to an optimal level to improve filtration performance.
The ability of air filter media to withstand operating pressures is typically dependent upon the pleat count, the pleat depth, the pressure drop of the media, loading capacity of the media, filter frame strength, bonding strength of the media to the frame, and the stiffness of the filter media. The filter media can become unsteady when air pressure is applied to one side. In the event the pleats deform or collapse, a portion of the surface area can be reduced and the pressure drop across the filter element will increase, further increasing the force applied to the filter media. Further, if the tips or peaks of the pleats do not remain in a straight line but instead become wavy, this may cause walls of the pleats to contact one another and to close off some of the surface area of the media. The end result is an increase in pressure drop and a reduction in dust holding capacity.
There is a need for an automated method of manufacturing a pleated filter that has good flow characteristics and exhibits sufficient stability so that the pleats do not collapse or deform when subjected to operating pressure.